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MG MGA - original MOWOG pistons

Hi Guys,

I had a crack in the water jacket that went right across between the core plugs. Repair was not economical (around 1,000 GBP) so I opted to take a gamble on a second hand engine that was completely seized but at 300GBP seemed a reasonable risk. After un-seizing it I noticed that not only was the overall condition of the casting very good, but that it also had pistons with MOWOG stamped on the top with other markings within a diamond. I'm guessing that these are the original pistons as fitted by the factory perhaps? I haven't measured them as yet.

If they are and they seem in reasonably good condition do you think it wise to reuse them in my rebuild or should I get new ones? I'm inclined to use them on the basis that original is always best. Appreciate any thoughts on this.

Best regards

Alan
AR Terry

Depends what state the bores are in, and the ring grooves. If any sort of boring is necessary then you will need new pistons.
Allan Reeling

" If any sort of boring is necessary then you will need new pistons."

Not if the bores are sleeved back to standard which was BMC practice with Gold & Silver seal engines.
Chris at Octarine Services

Usual place where engines seize is the bores. Are they OK?
Art Pearse

Thanks for comments guys. The block is in the machine shop at the moment being re-bored and sleeved back to original spec. My question is really about using what I think are the original pistons. Is age a potential problem i.e. metal fatigue or some other factor that I should consider.
Top tip for releasing a seized engine, hot cooking oil what you cook your chips in.

Regards
Alan
AR Terry

Alan
If you are going to all the trouble and expense of resleeving back to standard, I wouldn't even think of jamming crappy old 2nd hand x-seized pistons in it----------
William Revit

Willy you are most probably right and I have decided not to use them. I thought there may be a rarity value.
If they could be of use to anyone out there please let me know.
Thanks to all that have commented.
Best regards
Alan
AR Terry

Hi Alan,
some time ago I dropped a spring washer inside the top of the head. This spring washer fell down through the induction manifold. Needless to say the washer was caught between the head and the no. 2 piston. Not much damage was done to the combustion chamber, but the piston, being made of soft aluminium, was very badly damaged and I had to replace it. I now have 3 mowog pistons and one after market. I will be extremely grateful if you can let me have one of your mowog pistons, providing that they are std pistons. If you wish to contact me via email, my address is fcamill@hotmail.com

Frank
F. Camilleri

Hi Frank,
I'd be more than happy to send you one of the pistons. Will contact you on email.
Best

Alan
AR Terry

I had to replace my head gasket recently, so gave the piston heads a good clean in the process. I was surprised to discover that I've got 3 MOWOG pistons (presumably the originals) and one which is unmarked. Also, whereas the MOWOGS are slightly dished, with a small hole in the middle, the 'new boy' is completely flat with no hole. I don't know when or why one of the originals was replaced, but it must have been more than 45 years ago because that's how long I've owned her. I'm sure that most purists would say that I should replace the new boy with an original MOWOG, but it all works just fine so I think I'll leave it as it is.
Robert Sinclair

Robert

Surely that will give a slightly different compression on that cylinder? Can't be good for the engine or smoothness of running even though 45 years have gone by.

Steve
Steve Gyles

Horses and water Steve.

Alan
AR Terry

Yes, I think it's probably time to buy myself a compression tester to see how all 4 are performing ... unless of course Mrs S is struggling to think of something to give me for Christmas.
Here's a pic of one of the original MOWOGs next to the "new boy".

Robert Sinclair

This thread was discussed between 07/11/2017 and 10/11/2017

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